Recently, Cui Xintong, a doctoral student of the Smart Watershed Team at the Research Institute, an academic paper entitled “Nitrate losses from forest during snowmelt: An underestimated source in mid-high latitude watershed” in the high-impact environmental journal Water Research. Professor Ouyang Wei served as the corresponding author.
The export of nitrate from forest ecosystems plays a significant role in the global nitrogen (N) cycle and watershed water quality. Due to the combined effects of forest litter decomposition and spatiotemporal heterogeneity of watershed hydrology, it is challenging to investigate nitrate loss of forested watershed and its contributions. In mid-high latitude area, freeze-thaw cycle can cause fine root mortality and the physical destruction of litter, resulting in the increase of nitrate concentrations in forest soils. Snow melting in early spring promotes snowmelt runoff and removes large amounts of soluble N from the soil, exacerbating forest nitrate loss during the snowmelt season. Based on the continuous field sampling in the Tumen River watershed, combined with the modified watershed forest nutrient cycling simulation model, the research team investigated the characteristics of nitrate loss under freeze-thaw conditions in mid-high latitude forested watersheds, so as to precisely identify forest nitrate loss and its contribution to watershed loading.
The study found that nitrate loss from forest lands during the snowmelt season contributes positively to total watershed N loads, particularly in the upstream where contributed 8.18±3.94%, and the headwater stream contributed up to 16.48%. The primary drivers of forest nitrate loss in headwater areas are the snowmelt runoff in spring and high mineralization of soil organic N. Analysis of long-term sequence record of globally representative mid-high latitude forest plots or forest streams with similar climates indicated that the high nitrate flux occurs synchronously after extreme cold weather and soil freezing, and most observed forests exhibiting increased nitrate loss fluxes. Therefore, forest nitrate losses during the snowmelt season should be better characterized and included in future watershed N budgets, thereby providing a scientific basis for improving precise watershed water environment management.
This research was financially supported by National Natural Science Foundation of China (42271326), National Key R&D Program of Intergovernmental International Science and Technology Innovation Cooperation (2023YFE0100200), and the Supplemental Funds for Major Scientific Research Projects of Beijing Normal University, Zhuhai (ZHPT2023004).
Cited: Cui, X.T., Ouyang, Wei., Liu, L.H., et al. Nitrate losses from forest during snowmelt: An underestimated source in mid-high latitude watershed[J]. Water Research, 2024, 249: 121005.